Exemplary embodiments relate to an operating method of a semiconductor device and, more particularly, to a program method.
The operation of a semiconductor device is may be classified into program, read, and erase operations.
The program operation refers to an operation of raising the threshold voltage of a memory cell by supplying a high program voltage (for example, 20 V) to a word line coupled to the memory cell. The read operation refers to an operation of determining the program state of a memory cell according to whether the threshold voltage of the memory cell is higher than or lower than a verify voltage by supplying a read voltage to a word line coupled to the memory cell. The erase operation refers to an operation of lowering the threshold voltage of a memory cell by supplying an erase voltage to a well.
A memory cell that can be programmed in one state is called a Single Level Cell (SLC), and a memory cell that can be programmed in a plurality of states is called a Multi-Level Cell (MLC).
The MLC is being used in semiconductor devices because the MLC is more suitable for a higher capacity. A program operation of the MLC is described below.
FIGS. 1A and 1B are graphs illustrating a conventional program method. More specifically, a method of programming one memory cell with first, second, and third states P1, P2, and P3 is described below.
Referring to FIG. 1A, after all the memory cells of a specific memory cell block are erased, a Least Significant Bit (LSB) program operation is performed on a page (more specifically, a page is a group of memory cells coupled to the same word line) selected from among the pages of the memory cell block. The LSB program operation is performed to raise the threshold voltages of memory cells that are to be programmed with the second state P2 or the third state P3, which is higher than the second state P2, from among the memory cells included in the selected page. After the threshold voltages of the memory cells to be programmed with the second or third state P2 or P3 are raised, a Most Significant Bit (MSB) program operation is performed on the selected page.
The MSB program operation is performed to raise the threshold voltages of memory cells that are to be programmed with the first state P1 higher than an erase state ER, but lower than the second state P2 or the third state P3, from among the memory cells included in the selected page. More specifically, the threshold voltages of memory cells that are to be programmed with the first state P1 from among memory cells of the erase state ER are raised by performing the MSB program operation. Furthermore, the threshold voltages of memory cells that are to be programmed with the second state P2 or the third state P3 from among the memory cells on which the LSB program operation has been performed are raised by performing the MSB program operation.
Particularly, in the program operation to program memory cells in the third state P3, a high program voltage is used because the threshold voltages of relevant memory cells are stepwise raised from the erase state ER to the third state P3.
However, the threshold voltages of memory cells that have been programmed may be shifted because interference on memory cells adjacent to a selected word line is further increased according to an increase of a program voltage supplied to the selected word line. If the threshold voltages of the memory cells are shifted, data read out by a read operation may not be reliable.